This invention relates generally to anchor bolt assemblies of the expansion type adapted to fasten fixtures to masonry surfaces, and more particularly to an assembly which when installed in a hole drilled in the masonry is not only anchored in the hole but also acts to press the fixture against the masonry surface, thereby resisting displacement of the fixture.
It is frequently necessary to bolt fixtures and other heavy parts to the surface of brickwork, concrete and other forms of masonry. For this purpose, it is the conventional practice to make use of an anchor bolt assembly having an expansible shell which serves to securely retain the bolt within the masonry hole. Anchor bolt assemblies come in diverse forms; but in all such assemblies, some means are provided to bring about the dilation of an expansible shell or similar component against the wall of the masonry hole to anchor the bolt therein.
Typical of prior art expansion type anchor bolt assemblies is that disclosed in the Zefferer U.S. Pat. No. 3,742,809 in which the bolt has a conically-tapered rear end portion which cooperates with an expansion sleeve so that when the bolt is turned with a wrench or other torque-producing tool, the tapered rear end thereof advances into the expansion sleeve which is thereby forced outwardly to anchor the bolt in the masonry hole.
Anchor bolts of the type heretofore known are difficult to install properly in a manner whereby the bolt is not only anchored in the hole drilled in the masonry, but the head of the bolt is firmly pressed against the face of the fixture so that the fixture is not loose and cannot be displaced.
For example, in installing an anchor bolt of the Zefferer type which passes through a hole in the fixture into a hole in the masonry, the head of the bolt must be located away from the face of the fixture before the bolt is tightened. The installer must guess the amount of expansion that will be required of the expansion sleeve when turning the bolt to obtain the proper hold on the masonry, inasmuch as the head of the bolt must then be firmly in contact with the fixture being fastened when expansion is complete.
In practice, this is difficult to do; and in many cases, even though the bolt is anchored in the masonry hole, the head of the bolt is not in secure contact with the fixture, yet no further turning of the bolt is possible to tighten this contact. In this situation, which is often encountered with conventional anchor bolts, the fixture is loose and not properly fastened to the masonry.
The following prior art patents are of general interest in connection with anchor bolts:
McIntyre U.S. Pat. No. 4,056,037 PA1 Craig U.S. Pat. No. 332,701 PA1 Ploch U.S. Pat. No. 3,523,842 PA1 Polos U.S. Pat. No. 3,878,264 PA1 Polmon U.S. Pat. No. 3,270,793 PA1 McNulty U.S. Pat. No. 798,440 PA1 Lewis U.S. Pat. No. 2,667,099 PA1 Dempsey U.S. Pat. No. 2,988,950 PA1 Giannuzzi U.S. Pat. No. 3,766,819